Single-unit leadless EEG sensor

Abstract

Single-unit EEG sensors contain multiple closely spaced dry electrodes that can hook onto skin and associated electronic circuitry such as amplifiers, A/D convertors, wireless transmitters, and a power source such as a battery. The electrodes can be separated by about 20 mm or less, and the associated circuitry can be situated within a volume defined by the multiple electrodes. The single-unit sensors hook onto the skin using a tooth surface so that a rotation of the sensor secures and electrically connects the sensor to the skin.

We claim: 
     
       1. An EEG sensor, comprising:
 a housing having a circular perimeter and defining a cavity; 
 an EEG electrode assembly including at least three boot-shaped EEG electrodes fixed with respect to each other, wherein the at least three boot-shaped EEG electrodes are arcuate electrodes situated at the circular perimeter of the housing; 
 a differential amplifier situated within the cavity and coupled to the at least three boot-shaped EEG electrodes such that first and second boot-shaped EEG electrodes are coupled to respective differential amplifier inputs and a third boot-shaped EEG electrode is coupled to the differential amplifier as a reference so as to produce an output signal associated with the at least three boot-shaped EEG electrodes; and 
 a plurality of hooks situated on a distal surface of each of the boot-shaped EEG electrodes and operable to secure at least the three boot-shaped EEG electrodes to a surface of a subject, wherein a proximal surface of each of the boot-shaped electrodes defines a gap so that each of the boot-shaped EEG electrodes is adapted to conform to the surface of the subject. 
 
     
     
       2. The EEG sensor of  claim 1 , further comprising:
 an analog-to-digital convertor (ADC) coupled to an output of the differential amplifier so as to produce a digital signal corresponding to the differential amplifier output signal; and 
 a transmitter coupled to the ADC so as to produce a transmitted signal associated with the digital signal corresponding to the differential amplifier output. 
 
     
     
       3. The EEG sensor of  claim 2 , wherein the transmitter is a wireless transmitter. 
     
     
       4. The EEG sensor of  claim 1 , wherein the at least three boot-shaped EEG electrodes are situated on an exterior surface of the sensor housing. 
     
     
       5. The EEG sensor of  claim 1 , further comprising a switch coupled to the at least three boot-shaped EEG electrodes so as to select the first and second boot-shaped EEG electrodes to be coupled to the differential amplifier inputs and the third boot-shaped EEG electrode to be coupled as the reference. 
     
     
       6. The EEG sensor of  claim 1 , wherein the at least three boot-shaped EEG electrodes include a fourth boot-shaped EEG electrode, and further comprising an analog switch coupled to the four boot-shaped EEG electrodes so as to select the first and second boot-shaped EEG electrodes to be coupled to the differential amplifier inputs and the third and fourth boot-shaped EEG electrodes to be coupled as the reference. 
     
     
       7. The EEG sensor of  claim 3 , wherein the wireless transmitter is a radio-frequency transmitter and the electrodes are separated by less than 1 cm. 
     
     
       8. The EEG sensor of  claim 1 , further comprising:
 a substrate secured to the housing, wherein the at least three boot-shaped EEG electrodes are secured to the substrate and the substrate couples the at least three boot-shaped EEG electrodes to the amplifier. 
 
     
     
       9. The EEG sensor of  claim 1 , wherein the at least three boot-shaped EEG electrodes are fixed to a disposable disk substrate. 
     
     
       10. The EEG sensor of  claim 9 , wherein the differential amplifier is fixed to the housing, and the disposable disk substrate is removably secured to the housing. 
     
     
       11. An electrode assembly, comprising:
 a cylindrical substrate; and 
 at least three electrodes secured to the cylindrical substrate, each of the at least three electrodes having a toothed distal surface adapted for attachment to a skin surface, wherein the at least three electrodes are secured to a circular perimeter of a distal surface of the cylindrical substrate and each of the at least three electrodes includes an attachment portion coupled to the cylindrical substrate at the circular perimeter and an extension that extends from the attachment portion and defines a gap from the cylindrical substrate along at least a portion of the extension, and the toothed distal surface is a distal surface of the extension and includes a plurality of teeth. 
 
     
     
       12. The electrode assembly of  claim 11 , wherein the cylindrical substrate is a hollow cylindrical substrate. 
     
     
       13. The electrode assembly of  claim 11 , wherein the cylindrical substrate is a disk, and the at least three electrodes are secured to the disk so that the attachment portions extend from the disk along axes that are perpendicular to the disk. 
     
     
       14. The electrode assembly of  claim 11 , wherein the plurality of teeth and the extensions face in opposite directions. 
     
     
       15. The electrode assembly of  claim 11 , wherein each of the plurality of teeth have a plurality of gold-coated nanowires secured to the tooth surface. 
     
     
       16. The electrode assembly of  claim 15 , wherein the have a tooth depth of less than 0.5 mm and the cylindrical substrate has a diameter of less than 2 cm. 
     
     
       17. A method, comprising:
 securing an electrode assembly as recited in  claim 11  to electrically connect each of the at least three plurality of electrodes to the skin surface; 
 processing an electrical signal associated with at least three electrodes for transmission; and 
 transmitting the processed electrical signal from the electrode assembly. 
 
     
     
       18. The method of  claim 17 , wherein the electrode assembly is secured to the skin surface by rotation so that a toothed surface engages the skin surface, and wherein the electrical signal is processed so as to be transmitted as a digital signal. 
     
     
       19. The method of  claim 18 , wherein the processed electrical signal is transmitted as a radio-frequency signal. 
     
     
       20. The method of  claim 17 , further comprising selecting, from the at least three electrodes, first and second electrodes associated with the electrical signal to be processed for transmission, and a third electrode as a reference. 
     
     
       21. The method of  claim 17 , further comprising processing the electrical signal with an amplifier, and selecting, from the at least three electrodes, first and second electrodes to be coupled to amplifier signal inputs and a third electrode to provide a reference. 
     
     
       22. The method of  claim 21 , wherein the electrode selection is based on a signal magnitude or a signal to noise ratio of the processed electrical signal. 
     
     
       23. An electrode assembly, comprising: an electrode substrate; and at least three electrodes situated at a perimeter of the electrode substrate, each of the at least three electrodes having a distal surface having a toothed surface for attachment to a skin surface, wherein the toothed surface includes a plurality of teeth, each of the plurality of teeth having a plurality of gold-coated nanowires secured to the toothed surface.